Alpha synchrony and the neurofeedback control of spatial attention

During MEG neurofeedback training, subjects learned to manipulate the degree of alpha synchrony over the left versus right parietal cortex. The change in alpha synchrony was associated with a corresponding bias in visual processing and attention in the corresponding visual field. © 2019 Elsevier Inc. Decreases in alpha synchronization are correlated with enhanced attention, whereas alpha increases are correlated with inattention. However, correlation is not causality, and synchronization may be a byproduct of attention rather than a cause. To test for a causal role of alpha synchrony in attention, we used MEG neurofeedback to train subjects to manipulate the ratio of alpha power over the left versus right parietal cortex. We found that a comparable alpha asymmetry developed over the visual cortex. The alpha training led to corresponding asymmetrical changes in visually evoked responses to probes presented in the two hemifields during training. Thus, reduced alpha was associated with enhanced sensory processing. Testing after training showed a persistent bias in attention in the expected directions. The results support the proposal that alpha synchrony plays a causal role in modulating attention and visual processing, and alpha training could be used for testing hypotheses about synchrony.